Effect of Tableting Pressure and Geometrical Factor of Tablet on Dehydration Kinetics of Theophyline Monohydrate Tablets

The effect of compression pressure and geometrical factors (thickness and diameter) of tablet on the dehydration kinetics of theophylline monohydrate tablets was studied using an infrared water-content measuring instrument. The dehydration rate of 2 cm diameter tablets decreased with increase in tabletting pressure. The dehydration rates of tablets also depended on tablet shape. The 2 cm diameter tablets (thin tablets) dehydrated faster than 1 cm diameter tablets (thick tablets). Dehydration of the powder bed (loosely packed tablets) and 2 cm tablets compressed at 49 MPa followed the two-dimensional phase boundary equation, and that of 2 cm diameter tablets compressed at 98 MPa and 196 MPa (thin tablets) followed the three-dimensional phase boundary equation. Dehydration of 1 cm diameter tablets compressed at 98 MPa (thick tablets) followed the one-dimensional diffusion equation. It seems that the dehydration of the tablet was controlled by the porosity and the surface area of the tablet. Therefore, tablet thickness and tabletting pressure are important factors affecting the dehydration mechanism.     

Effect of the Manganese Valence State on the Electrical Conductivity of Barium Titanate

The effect of defect structure on electrical conductivity for Mn-doped BaTiO₃ at high temperatures was studied experimentally and theoretically. The measured conductivity was proportional to P_o2^−1/4 in the n -type region, and to P _o2^+1/6 in the p -type region in the temperature range between 900° and 1000°C. The results agree with calculations on the basis of the equilibrium equation for the valence change of Mn ions between tetravalent and trivalent. In the p -type region, the concentration of trivalent Mn ions decreases with P _o2^−1/6.     

Direct excitation of xenon by ballistic electrons emitted from nanocrystalline‐silicon planar cathode and vacuum‐ultraviolet light emission

Abstract— To verify the possible use of energetic electrons for direct excitation of inert gas molecules, a nanocrystalline‐silicon (nc‐Si) planar ballistic emitter is operated in a high‐pressure xenon gas ambience. Under the pulse drive, vacuum‐ultraviolet (VUV) light emission is detected without any signs of discharge. The transient behavior of the VUV light emission properly corresponds to that of the nc‐Si emitter. In accordance with quantitative analyses of electron‐emission characteristics and the VUV output, the electron‐to‐photon conversion efficiency reaches 81% in the relatively efficient emitter case. The VUV output power is mainly determined from the number of electrons with energies compatible the with internal excitation of xenon. The emission spectrum observed at a pressure of 10 kPa shows peaks at 152 and 172 nm, which are thought to be originated from metastable Xe²* states. In contrast to the case of conventional impact ionization, no near‐infrared (NIR) peaks are seen in the spectrum. These results strongly suggest that the incidence of energetic electrons causes direct excitation of xenon molecules followed by radiative relaxation through intermediate states. The generated VUV light can be easily converted to visible light using a phosphor screen. As a discharge‐free VUV light emission, this phenomenon is potentially applicable to mercury‐free, high‐efficacy, and high‐stability flat‐panel light‐emitting device.     

Variation of ATP content in Scenedesmus dimorphus cells grown in a chemostat culture and its comparison with chlorophyll-A content

The variations of ATP and chl-a contents in Scenedesmus dimorphus cells grown in a chemostat culture under nutrient limitation were investigated. ATP and chl-a contents per algal dry weight varied in the ranges of 0.15–1.64 μg mg⁻¹ (0.33–3.82 μg mg⁻¹ as ATP/C ratio) and 0.32–1.32% (7.8–30.8 μg mg⁻¹ as chl-a/C ratio), respectively, under the conditions of T-N/T-P ratio of 2–50 by weight and dilution rate of 1–4 per day. At every T-N/T-P ratio, both ATP and chl-a contents increased as dilution rate increased. At a given dilution rate, ATP content decreased systematically as T-N/T-P ratio increased, with the only exception at dilution rate of 4 per day. It was considered based on the result that ATP or chl-a can hardly be used successfully as an indicator of algal biomass.     

A new family of NAD(P)H-dependent oxidoreductases distinct from conventional Rossmann-fold proteins

A new family of NAD(P)H-dependent oxidoreductases is now recognized as a protein family distinct from conventional Rossmann-fold proteins. Numerous putative proteins belonging to the family have been annotated as malate dehydrogenase (MDH) or lactate dehydrogenase (LDH) according to the previous classification as type-2 malate/L-lactate dehydrogenases. However, recent biochemical and genetic studies have revealed that the protein family consists of a wide variety of enzymes with unique catalytic activities other than MDH or LDH activity. Based on their sequence homologies and plausible functions, the family proteins can be grouped into eight clades. This classification would be useful for reliable functional annotation of the new family of NAD(P)H-dependent oxidoreductases.     

An integral equation method for non-self-adjoint eigenvalue problems and its applications to non-conservative stability problems

The aim of the work reported in this paper is to present the new formulation of the integral equation method for non-self-adjoint problems and to apply the method to stability problems of elastic continua subjected to non-conservative loadings. A general non-self-adjoint eigenvalue problem stated in terms of differential operators is transformed into a set of coupled integral equations. Our derivation of integral equations is based on an inverse formulation of a canonical form for the original problem and the corresponding fundamental solution pair. Three well-known non-conservative stability problems in elasticity are examined by this integral equation method as illustrative examples. The approximate values of the critical parameters of sample problems demonstrate a sufficient accuracy through a comparison of other values.     

Computer-assisted automatic synthesis II. Development of a fully automated apparatus for preparing substituted N–(carboxyalkyl)amino acids

A versatile automated apparatus, equipped with an artificial intelligence has been developed which may be used to prepare and isolate a wide variety of compounds. The prediction of the optimum reaction conditions and the reaction control in real time, are accomplished using novel kinetic equations and substituent effects in an artificial intelligence software which has already reported [1]. This paper deals with the design and construction of the fully automated system, and its application to the synthesis of a substituted N-(carboxyalkyl)amino acid. The apparatus is composed of units for perfoming various tasks, e.g. reagent supply, reaction, purification and separation, each linked to a control system. All synthetic processes including washing and drying of the apparatus after each synthetic run were automatically performed from the mixing of the reactants to the isolation of the products as powders with purities of greater than 98%. The automated apparatus has been able to run for 24 hours per day, and the average rate of synthesis of substituted N-(carboxyalkyl)amino acids has been three compounds daily. The apparatus is extremely valuable for synthesizing many derivatives of one particular compound structure. Even if the chemical yields are low under the optimum conditions, it is still possible to obtain a sufficient amount of the desired product by repetition of the reaction. Moreover it was possible to greatly reduce the manual involvement of the many syntheses which are a necessary part of pharmaceutical research.     

Experimental study and kinetic analysis on sodium oxide–silica reaction

ABSTRACT

In a sodium-cooled fast reactor (SFR), if considering hypothetical severe accidental condition such as the steel liner failure of structural concrete caused by intensive leakage of liquid sodium (Na) coolant, the liquid sodium–concrete reaction (SCR) may take place. The major consequences of SCR are hydrogen release, energy release and concrete ablation. Thus, it is important to understand the phenomenology and kinetic behavior of SCR. As a part of a series of studies on SCR, this study focused on the reaction between sodium oxide (Na₂O) and silica (SiO₂), which is dealt with possible formation of Na₂O as the result of sodium–water reaction in the initial stage of SCR. Through thermoanalytical and X-ray diffraction measurements, it was revealed that Na₂O–SiO₂ reaction to form sodium orthosilicate (Na₄SiO₄) occurs at significantly lower temperature in comparison with Na–SiO₂ reaction. The reaction is kinetically characterized as a largely overlapping multistep reaction, which is composed of at least three reaction steps. On the basis of the observations, the impact of Na₂O–SiO₂ reaction in the overall SCR and the significance of the conventional kinetic analysis using the Kissinger method are discussed.     

Noise-driven numerical irreversibility in molecular dynamics technique

It is widely believed that, in molecular dynamics (MD) simulations, round-off errors can cause numerical irreversibility since, in the standard MD, floating-point real number arithmetic is employed and round-off errors cannot be avoided. To investigate the characteristic of this numerical irreversibility, the ‘bit-reversible algorithm’, which is completely time-reversible and is free from any round-off error, is made use of as a test bed. Through this study, it is clearly demonstrated that, other than the extent of the stability of the system, the appearance of irreversibility is related to the ‘quantity’ of the controlled noise. By means of the bit-reversible simulation added to the controlled noise of an appropriate ‘quantity’, the characteristic of the numerical irreversibility in the standard MD is revealed.